1. Android
Looking beyond the obvious
10/20/11
Cocoaheads Siegen
Dipl. Inform. Simon Meurer

2. Agenda
● General
● Android „Desktop“
● Developer's View
● Publishing
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3. What is Android?
● OS and Software-platform for different Mobile
Devices
● Developed by Open Handset Alliance
● Based on Linux-Kernel 2.6
● Biggest rival of iOS on Smartphone OS-Market
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4. Market share
50
45 43,4
40
35
30
25
22,1
20
18,2
15
11,7
10
5
1,9 1,6 1
0
Android Symbian iOS RIM Bada Microsoft Others
2nd quartal 2011 Market share (%) - source: Gartner
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5. Sample Devices
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6. Android Versions
● 2.x – for mobile phones (act. 2.3.6)
● 3.x – for tablets (act. 3.2)
● 4.x – gets 2.x and 3.x together
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7. Android „Desktop“
● Apps in Menu
●Can be moved to „Desktop“
● Themes and Live-Background
● Shortcuts
● No. of Desktops set by Theme
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8. Widgets
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9. Notifications and Preferences
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10. Developer's View
● Architecture
● Language
● Key Concepts
● Menues
● Environment
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11. Architecture
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12. Language
● Android is Java, right?
Yes, but:
● No Constructors (for GUI-Classes)
● No Swing or SWT
● No System.out.println(...)
● Limited memory
● ...
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13. Key Concepts
● Activities
● Layouting with XML
● Intents
● Services
● Content Providers
● Resources
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14. Activities
● UI-Screen (better: logic)
● An app has usually more than one
● Activity Stack
● New Activities pushed on stack
● Back pops them of
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15. Example (HelloWorldActivity.java)
package com.test.helloworld;
import android.app.Activity;
import android.os.Bundle;
public class HelloWorldActivity extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
}
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16. Layouting with XML
● GUI is build in XML
● Tags = Elements, Attributes = Properties
● Different Resolutions possible
→ No Absolute Layout, instead:
●LinearLayout, RelativeLayout, TableLayout,
…
● Place in XML = Place in Layout
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17. Example (main.xml)
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView android:id="@+id/textview" android:layout_width="fill_parent"
android:layout_height="wrap_content" android:text="Hello World!" />
<Button android:id="@+id/button" android:layout_height="wrap_content"
android:layout_width="match_parent" android:text="Hello" />
</LinearLayout>
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18. HelloWorld
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19. Clicking the button
public class HelloWorldActivity extends Activity {
public void onCreate(Bundle savedInstanceState) {
...
Button b = (Button) findViewById(R.id.button);
b.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
Toast.makeText(HelloWorldActivity.this, "Hello World!",Toast.LENGTH_SHORT).show();
Log.v("HelloWorldActivity", "Hello clicked");
}
});
}
}
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20. Toasting and Logging
● Toast
●displaying short Text for a short while
● NOT for debugging
● Log
● is for logging on console
● Different levels:
– d, e, i, v, w
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21. So, what about other Activities?
● Problem: No Constructors for GUI-Classes
→ Intent:
● Describes a spec. Action
● e.g. „pick a photo“, „take a picture“, „create
person“
● Standards: „send an email“, …
● Can be registered as standard
● Intents extras = Values of Constructors
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22. Example (Intents)
onClick of Hello-Button:
Intent i = new Intent(HelloWorldActivity.this, HelloWorldActivity2.class);
i.putExtra("Hello", "World");
startActivity(i);
HelloWorldActivity2:
public class HelloWorldActivity2 extends Activity{
protected void onCreate(Bundle savedInstanceState) {
...
TextView t = (TextView) findViewById(R.id.textview2);
t.setText(getIntent().getStringExtra("Hello"));
}
}
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23. How do I get results?
1.startActivityForResult(Intent, requestCode)
2.Generate result and put it in the intent
3.set resultCode and finish() the activity
4.in onActivityResult(requestCode, resultCode,
Intent data) is your result
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24. Services
● Task that runs in background
● e.g. Music Player
● Can be started by Activity1
● Changed by Activity2
– e.g. Activity2 says „stop“ or „nextTrack“
● „Live Wallpaper“
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25. Resources
● Manage data with xml
● Resource-Class is generated automatically
●holds ids for the elements
● Contains:
● Layouts, Strings, Images, Values, Menus,
Settings
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26. Menu, Contextmenu and Search
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27. Development environment
● Recommended: Eclipse
● Fully integrated:
● GUI-Builder
● XML-“Helper“
● Console
● Debugging-Tools
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28. GUI-Builder
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29. XML-“Helper“
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30. Console and Debugging-Tools
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31. Where do I publish my App?
● Android Market:
●510,000 Apps in Sept. 2011
● uses Google Checkout for billing
● takes 30% of the app-price
● Until now:
● No controlles!
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32. Publishing on Android Market
Requirements:
● Google Account
● register as developer on developer.android.com
●pay 25$
● only Creditcards
● For charged apps:
● register at Google Checkout
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33. Publishing on Android Market
Requirements for the App:
● App must be signed
●expires after 22.10.2033
● AndroidManifest.xml:
● android:versionCode and
android:versionName must be defined
● android:Icon and android:label must be
defined
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34. Publishing without Android Market
● Complete free:
●Generate .apk
● Put .apk on your website
● .apk must be copied to device and installed
(e.g. with APK-Manager)
● Problems:
● No (normal) User will do that!
● Billing, integration, updates
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35. Publishing without Android Market
● Alternative Markets:
●Amazon App Store (about 18,000 Apps)
● SlideME (about 10,000 Apps)
● AndAppStore (about 2,000 Apps)
● OnlyAndroid
● But:
● Google can delete your app at any time!
● Not so many customers
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36. Lessons learned
● Android is NOT Java
● XML-Layouting is not allways fun
● Complicated solutions for simple problems
● Intents are sometimes mysterious
● Looks half-baked sometimes
● Docu is not as good as iOS-Docu
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37. But...
● Costs:
●Development for free
● Publishing 25$ once
● Market share
● Mainly Java
● Freedom of choice
...
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